In a previous top operated railway tank car lading valve assembly, a rod 10 (FIG. 1) extends to the top of a railway tank car (not shown) and is operated at the top of the tank in a known manner. The rod 10 is attached to a sleeve 12 with a pin 14 in a known manner. The stem is externally threaded at 16 and engages a sleeve 18 which is internally threaded as indicated at 20. The sleeve 18 includes a slot 22 which engages a flange portion 24 of a valve cage 26 with clearance as indicated at 28. In addition, a keeper 30 holds the sleeve 18 in engagement with the cage 26 by means of a horizontally extending pin 32 as shown in FIG. 2.
However, it will be apparent that the clearance 28 allows horizontal and rocking movement to occur between the cage 26 and the sleeve 18. This results in a tendency for the stem 16 and the sleeve 18 to become cocked and thus the threads 16 and 20 become bound and it is not possible to operate the valve from the top.
Fasteners 34 extend through the cage 26 and into a tank car bottom outlet mounting flange indicated at 36. The cage 26 includes a valve seat 38 having an inclined seat surface 40. A valve closure 42 includes a retaining portion 44 having a formed slot 46 which engages the lower end 48 of the valve stem 16 with a considerable amount of clearance indicated at 50. The clearance 50 allows movement of the stem 16 relative to the valve closure 42. This clearance also contributes to the likelihood that the stem will become cocked relative to the closure 42 and thus make the valve inoperable from the top of the tank.
The valve closure 42 further includes a slot 52 into which is placed a seal 54. Some sticky ladings tend to pull seat 54 out of slot 52. A depending valve guide 56 is held in place with a threaded pin 58 which threadably engages the valve as indicated at 60 and is held in place with a nut 62. The guide 56 also maintains the seal 54 in place.
As is conventional, the outlet chamber 70 is attached to flange 36 with fasteners 71. A tongue 72 engages a slot 73 containing a seal 74. The outlet chamber includes a hollow lading discharge portion 75 which is closed by a cap 76 which includes a removable plug 77. Cap 76 is adapted to receive a suitable chain 78 to prevent the loss of the cap as is known in the art. Breakage groove 79 may also be provided between the cap and the bottom of the hollow chamber 75.